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In this study, the neutral scalar thermal model is presented for single-phase and so, a single-phase Rayleigh–Bénard is investigated. The Shan-Chen model is expressed in the isothermal state, and by combining the two models, the mixed Shan-Chen thermal method is presented. Then, using a mixed model, a two-phase Rayleigh–Bénard with the thermal Shan-Chen method is proposed. Two-phase Rayleigh–Bénard convective heat transfer is simulated at the relatively high Rayleigh numbers (105), different Capillary numbers (10−3 to 10−4), and also, various ε parameters (parameters related to the temperature difference and thermal expansion). In two-phase Rayleigh–Bénard convective heat transfer increasing the Rayleigh number leads to the increment of Rayleigh–Bénard convective heat transfer between the hot and cold wall and the temperature gradient enhances in the vicinity of the upper wall, lower wall, and interface. It is worth mentioning, that in the two-phase Rayleigh–Bénard problem, the variations of the interface are changed only by changing the thermal expansion coefficient and the temperature difference between the two walls. The results show that the mixed model can simulate two-phase thermal flows. The stability of this method is the same as the multi-phase isothermal models, and it can be applied well for different state equations and relatively high Rayleigh numbers.

Background: In this research, the effect of anode and cathode channel cross-sectional shape on the performance of PEM fuel cell was investigated and the appropriate length and dimensions of the channel were determined. Finally, for the determined geometric conditions, the cell performance at different voltages was investigated. Methods: The purpose of this study was to investigate the structural characteristics of the fuel cell on its performance. The results show that the pressure and temperature in the catalyst layer (CL) of the cathode side are greater than the anode, and the temperature in the central regions of the catalyst layer is higher than the lateral regions. Also, the channel with a length of 100 mm is optimal in terms of producing the maximum current density and the amount of pressure drop is much lower than the channel with a length of 150 mm, which reduces the power consumption of the cell. Significant findings: In general, a higher electric current is produced by increasing the thickness of the gas diffusion layer (GDL) and the catalyst layer. At a voltage of 0.8 V, with increasing thickness from 0.25 mm to 0.5 mm, the current density increases above 6 %. The percentage increase in current density at 60 °C–80 °C for 0.85 V and 0.75 V voltages is 42.1 % and 9.28 %, respectively.

Fossil fuels cause global warming and create greenhouse gases that cause irreparable environmental damage. On the other hand, because the combustion reactions are not completely done, dangerous compounds, such as nitrogen or carbon monoxide are produced which are very toxic and dangerous. As a result, innovative methods were implemented in combustion processes. One such method is to use a catalyst during the combustion process. This study used a molecular dynamics method to examine how the concentration of CuOCeO2 catalyst affected air-methane combustion in a helical microchannel. The results show that the maximum (Max) values of density (Dens), velocity (Velo), and temperature (Temp) in the excess oxygen (EO) state were 0.142 atoms per second, 0.35 Å/ps, and 1089 K, respectively, when the atomic ratio of CuOCeO2 increased from 1 % to 4 %. Subsequently, these values exhibited a declining trend. Also, the values of heat flux (HF), thermal conductivity, and combustion efficiency in 4 % catalyst reached the max values of 2038 W/m2, 1.15 W/m·K and 88 %. The results related to the max values of Dens, Velo, and Temp for the oxygen deficiency state had a similar trend and increased to the max values of 0.103 atom/Å3, 0.41 Å/ps, and 1024 K in 4 % catalyst, and then decreased by increasing the catalyst ratio of CuOCeO2 and reaching 10 %. The thermal behavior of nanostructure was more optimal in the deficient oxygen medium.

This study employed molecular dynamics simulations to investigate water transport through a carbon nanotube under an electric current, focusing on how varying ion atomic ratios influence key system parameters. These parameters include electric current intensity, fluid current intensity, maximum density, hydrogen bond count, and interaction energy as ion concentration changed. The research aimed to examine the effects of these changes on ion mobility, water permeability, and ion–carbon nanotube interactions. The study is conducted in two phases: equilibration, followed by the analysis of atomic transformations and the creation of various atomic ratios in samples. In the first phase, the kinetic energy of the atomic sample converges to 0.162 eV, and the potential energy reaches to 2.048 eV after 10 ns, indicating limited structural mobility and attractive forces among atoms. After equilibration, we achieved the atomic transformation process and created different atomic ratios. The results indicate that increasing ion ratios in the fluid led to a rise in electric current intensity, from 5.31 to 5.52 e/ns. Higher ion concentrations resulted in a greater density of charge carriers, enhancing ionic mobility and ion transport through the carbon nanotube. Moreover, higher ionic concentrations not only reduced the maximum density from 4.83 to 4.65 atoms/nm³ but also increases the number of broken hydrogen bonds, which could impact water transport and flow dynamics. Finally, according to the findings, there are 133 broken hydrogen bonds instead of 116, and the strength of the nanofluid flow, as well as the electric current, both increased when the ionic percentage of atoms rose to 5 %.